Remote execution of commands is well known, for example in spacecraft, virtual desktop user interfaces, client-server applications, and the like. In general, a useful remote command execution system over an open network, such as Internet email, requires user authentication, and typically some form of feedback to confirm status. Further, a sequence of commands often requires conveyance of the state between commends, and a subsequent command may depend on the results of an earlier command.
In many networks, a bidirectional communication protocol is implemented, such that secure communications can be negotiated, for example using PKI techniques, to assure that the communications are not intercepted, and thus expose the system to unauthorized access. Therefore, a simple username-password combination passed in cleartext format is insecure, and exposes the execution system to security risks. On the other hand, without execution of a complex algorithm, which cannot be assured on a generic remote client, it is difficult to provide a dynamic password, such that an eavesdropper could not capture the password and resend the message in modified form to take control of the target system.